A conventional air-conditioning system comprises a compressor for compressing and delivering a refrigerant for a refrigerating cycle. A condenser condenses the high-pressure refrigerant delivered from the compressor. An expansion valve throttles the refrigerant condensed and liquefied in the condenser. An evaporator heat-exchanges the low-pressure liquefied refrigerant throttled by the expansion valve with air blowing into interior of a vehicle and evaporates the refrigerant to cool the air blowing into the vehicle through a heat absorption action caused by evaporation latent heat of refrigerant. Refrigerant pipes connect the above listed elements.
FIGS. 1A and 1B illustrate a structure of a roof-on type air conditioner for a bus. A discharging process of cooled air is described with reference to a circulation flow of refrigerant in the air-conditioning system as below. If a static pressure is generated in an evaporator motor, air inside the vehicle is introduced into an evaporator core 1, and a liquid-phase refrigerant flowing in the evaporator core 1 absorbs heat from the interior of the vehicle air and becomes a gaseous state.
Thus, air passing through the evaporator becomes cold, and the cooled air can be supplied inside an entire space of the vehicle through a flow passage in an air conditioner duct 2.
In above conventional air conditioner, however, when the air conditioner is operated, the refrigerant flows in the entire evaporator core regardless existence of a passenger and whether or not the passenger is on a specific area inside the vehicle, thus increasing power loss of an engine and deteriorating fuel efficiency.
The above structure described as the background art is provided for only understanding the background of the present disclosure, however it should not be accepted that the inventor recognizes that the present invention corresponds to the conventional art which has been already well-known to one having an ordinary skill in the art.